Redox modulation of luminescence : association of ruthenium organometallics and luminescent units – RuOxLux

The originality of this project relates to the use of multifunctional compounds based on redox active carbon-rich organometallics associated with luminophore units.

With the help of associations between Eu3+, Yb3+, Nd3+ ions and low potential redox active ruthenium carbon-rich complexes bearing bipyridine chelating unit(s) of the type trans-[Ph-C?C-(dppe)2Ru-C?C-bipy-?2-N,N’-Ln(TTA)3)], trans-[(dppe)2Ru(-C?C-bipy-?2-N,N’-Ln(TTA)3)2], trans-[Ph-C?C-(dppe)2Ru-C?C-C6H4-C?C-bipy-?2-N,N’-Yb(TTA)3)], we built new original d-f heterometallic complexes. Efficient sensitization in the visible range of the Nd3+ and Yb3+ near-infrared (NIR) emitters was achieved with the metal-acetylide antenna, while sensitization of the Eu3+ ion was not efficient owing to a too low energy level of the antenna excited state. The redox properties of these groups also allows for low potential redox modulation of NIR luminescence of the Yb3+ ion and, for the first time, of the Nd3+ ion.

This work will permit to consecutively achieve, evaluate and rationalize electro-modulation of luminescence with this original approach based on the use of ruthenium organometallics.

«Lanthanide sensitization with Ruthenium Carbon-Rich Complexes and Redox Commutation of NIR Luminescence.»
L. Norel, E. Di Piazza, M. Feng, A. Vacher, X. He, T. Roisnel, O. Maury, S. Rigaut Organometallics doi :10.1021/om500059d

The aim of the project is to develop novel fundamental issues for optically switching molecular materials, with a rarely used strategy based on electro-modulation of luminescence. Electro-modulation of luminescence combines several advantages over other types of modulations: contactless photo-activation with specific and flexible addressing (energy, intensity), high sensitivity, use of orthogonal signals (electron and photon) avoiding destructive interfering readout. The originality of this project relates to the use of multifunctional compounds based on redox active carbon-rich organometallics associated with luminophore units. The ruthenium compounds are particularly suitable as they display intense absorption bands and promote exceptionally efficient intramolecular electronic communication in different redox states. As an ultimate result, our strategy should allow the achievement of stable emissive systems with efficient sensitization processes and an efficient control of luminescence at low-voltage. Therefore, original systems will be designed and through experimental and theoretical studies, their luminescent and switching abilities will be explored via the tuning of emission properties with light or electron transfer. These systems will be also designed to be integrated in electrochemical cells for the building smart operating devices suitable for molecular optoelectronics.
This proposal is composed of three connected parts with objectives of increasing complexity:
(1) The combination of metal acetylides [Cl(dppe)2Ru(-C=C-R)] with organic triarylamines will be directed to the search of strong through-bond interactions at the molecular scale. With such edifices, innovative electro-modulation of the emitted energy (wavelength modulation) via charge transfer change upon oxidation of the organometallic unit and/or intensity modulation is targeted.
(2) The further combination of metal-acetylides [Cl(dppe)2Ru(-C=C-R’)] or metal allenylidenes [Cl(dppe)2Ru(=C=C=CR’’2)]+ (R’ and R’’ including chelating units) with lanthanide ions will provide an original mean to get redox modulation of luminescence intensity up to the NIR range. The realization of multifunctional objects based on parallel electro- and photo-modulations will be also targeted with the insertion of a bistable photochromic dithienylethene moiety. This approach will provide unique molecular switches with two possible writing processes (light and electron transfer).
Full understanding of the involved processes with regard to the chemical structures is a crucial point for further tailoring and improvement of the systems. To this end, quantum chemical studies will be performed on the targeted complexes in these first two objectives.
(3) Application of these new objects to the building of luminescent switching devices operating at low potential will be achieved either in solution (thin layer), as deposited thin film, or via surface engineering with their grafting on conducting surfaces. The control of the connections between the molecular-scale components and the transposition of properties from solution to solid-state are crucial issues that will be considered.
Importantly, this interdisciplinary project will combine expertise from complementary partners with skills in synthesis, physical-chemistry, thin film chemistry, theoretical chemistry and photophysics. Therefore, the four planned tasks (i.e. system synthesis, system evaluations, device elaborations, and quantum studies) will permit to consecutively achieve, evaluate and rationalize electro-modulation of luminescence with this original approach based on the use of ruthenium organometallics.